I like that it is simple to use with no code needed at all! You can easily add new styles or remove existing ones by simply clicking buttons instead of writing any CSS yourself.
The only downside would be if there was an option where we could customize colors more than just black/white (maybe even multiple shades). We are solving our cross-browser compatibility issues in one place - everything looks great across browsers now because we don't have so many different files scattered around the server which makes maintenance easier overall as well since they're not being updated separately anymore when changes happen elsewhere.